boolProp allow45DegreeAngleOfRotation [true/false] (rotate with . and ,)
boolProp snapObjectsToGrid [true/false] allows you to place objects outside of the grid
Moveobjects on/off lets you place objects where they normally won't go.
Here's a list of cheats 
If you have M&G, you could probably also try this:
setQuartertilePlacement on/offHaven't tried that one yet, so I'm not sure what it does.